Soil carbon: A measure of ecosystem response in a changing world?

2005 ◽  
Vol 85 (Special Issue) ◽  
pp. 467-480 ◽  
Author(s):  
H. H. Janzen
Keyword(s):  
Agricultural Soils ◽  
Global Carbon Cycle ◽  
Ecosystem Response ◽  
Soil C ◽  
Four Dimensions ◽  
C Storage ◽  
C Dynamics ◽  
C Cycle ◽  
Global Carbon

The global carbon (C) cycle is changing, as evident from abrupt increases in atmospheric CO2. These changes have sparked interest in agricultural soils as potential repositories for excess atmospheric C. Our perspective on soil C, therefore, has shifted: once, we focused mainly on how soil C affected productivity within agroecosystems; now we see also how C dynamics in agricultural soils exert influences far beyond the farm. We have long used soil C as an indicator of soil quality; now we may want to use soil C also as a broader indicator of ecosystem response. To prompt further discussion, I offer some tentative thoughts about how we might use soil C as an indicator on a changing earth. They include: using soil C to measure changes across time, not only across space; devising more sensitive measures of soil C change; quantifying soil C across four dimensions; measuring the nature of C, as well as its amount; using soil C alongside other indicators; finding better ways of admitting our uncertainty; establishing long-term sites for our successors to measure soil C change; and following flows of C past the farm fences. Recent worries about global warming have focused our attention on “sequestering” soil C to remove atmospheric CO2. That aim may be worthy, but perhaps too narrow; a broader goal might be to ensure the productivity, permanence, and health of our agroecosystems and adjacent environments – and use C storage as a measure of progress toward that goal. Key words: Soil organic matter, global carbon cycle, carbon sequestration, global change

Post-thinning soil organic matter evolution and soil CO2 effluxes in temperate radiata pine plantations: impacts of moderate thinning regimes on the forest C cycle

2012 ◽  
Vol 42 (11) ◽  
pp. 1953-1964 ◽  
Author(s):  
Irene Fernandez ◽  
Juan Gabriel Álvarez-González ◽  
Beatríz Carrasco ◽  
Ana Daría Ruíz-González ◽  
Ana Cabaneiro
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Radiata Pine ◽  
Soil Samples ◽  
Mitigation Strategies ◽  
Change Scenario ◽  
Soil C ◽  
C Storage ◽  
C Cycle ◽  
C And N

Forest ecosystems can act as C sinks, thus absorbing a high percentage of atmospheric CO2. Appropriate silvicultural regimes can therefore be applied as useful tools in climate change mitigation strategies. The present study analyzed the temporal changes in the effects of thinning on soil organic matter (SOM) dynamics and on soil CO2 emissions in radiata pine ( Pinus radiata D. Don) forests. Soil C effluxes were monitored over a period of 2 years in thinned and unthinned plots. In addition, soil samples from the plots were analyzed by solid-state 13C-NMR to determine the post-thinning SOM composition and fresh soil samples were incubated under laboratory conditions to determine their biodegradability. The results indicate that the potential soil C mineralization largely depends on the proportion of alkyl-C and N-alkyl-C functional groups in the SOM and on the microbial accessibility of the recalcitrant organic pool. Soil CO2 effluxes varied widely between seasons and increased exponentially with soil heating. Thinning led to decreased soil respiration and attenuation of the seasonal fluctuations. These effects were observed for up to 20 months after thinning, although they disappeared thereafter. Thus, moderate thinning caused enduring changes to the SOM composition and appeared to have temporary effects on the C storage capacity of forest soils, which is a critical aspect under the current climatic change scenario.

scholarly journals Causes and timing of future biosphere extinctions

2006 ◽  
Vol 3 (1) ◽  
pp. 85-92 ◽  
Author(s):  
S. Franck ◽  
C. Bounama ◽  
W. von Bloh
Keyword(s):  
Global Carbon Cycle ◽  
Temperature Tolerance ◽  
Cambrian Explosion ◽  
Strong Decrease ◽  
The Earth ◽  
Reverse Sequence ◽  
Different Types ◽  
Global Surface ◽  
Global Carbon

Abstract. We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the combined ocean and atmosphere reservoir. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. During the entire existence of the biosphere procaryotes are always present. 2 Gyr ago eucaryotic life first appears. The emergence of complex multicellular life is connected with an explosive increase in biomass and a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. In the long-term future the three types of biosphere will die out in reverse sequence of their appearance. We show that there is no evidence for an implosion-like extinction in contrast to the Cambrian explosion. In dependence of their temperature tolerance complex multicellular life and eucaryotes become extinct in about 0.8–1.2 Gyr and 1.3–1.5 Gyr, respectively. The ultimate life span of the biosphere is defined by the extinction of procaryotes in about 1.6 Gyr.

scholarly journals Influence of climate change factors on carbon dynamics in northern forested peatlands

2006 ◽  
Vol 86 (Special Issue) ◽  
pp. 269-280 ◽  
Author(s):  
C. C. Trettin ◽  
R. Laiho ◽  
K. Minkkinen ◽  
J. Laine
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Management Practices ◽  
Atmospheric Temperature ◽  
Soil C ◽  
Altered Hydrology ◽  
Biogeochemical Models ◽  
C Dynamics ◽  
C Balance ◽  
C Cycle

Peatlands are carbon-accumulating wetland ecosystems, developed through an imbalance among organic matter production and decomposition processes. Soil saturation is the principal cause of anoxic conditions that constrain organic matter decay. Accordingly, changes in the hydrologic regime will affect the carbon (C) dynamics in forested peatlands. Our objective is to review ecological studies and experiments on managed peatlands that provide a basis for assessing the effects of an altered hydrology on C dynamics. We conclude that climate change influences will be mediated primarily through the hydrologic cycle. A lower water table resulting from altered precipitation patterns and increased atmospheric temperature may be expected to decrease soil CH4 and increase CO2 emissions from the peat surface. Correspondingly, the C balance in forested peatlands is also sensitive to management and restoration prescriptions. Increases in soil CO2 efflux do not necessarily equate with net losses from the soil C pool. While the fundamentals of the C balance in peatlands are well-established, the combined affects of global change stressors and management practices are best considered using process-based biogeochemical models. Long-term studies are needed both for validation and to provide a framework for longitudinal assessments of the peatland C cycle. Key words: Peatland, carbon cycle, methane, forest, wetland.

scholarly journals Through enhanced tree dynamics carbon dioxide enrichment may cause tropical forests to lose carbon

2004 ◽  
Vol 359 (1443) ◽  
pp. 493-498 ◽  
Author(s):  
Christian Körner
Keyword(s):  
Tropical Forests ◽  
Forest Dynamics ◽  
Forest Inventories ◽  
C Storage ◽  
Theoretical Approaches ◽  
C Cycle ◽  
Net Uptake ◽  
And Storage ◽  
Biodiversity Effects

The fixation and storage of C by tropical forests, which contain close to half of the globe's biomass C, may be affected by elevated atmospheric CO 2 concentration. Classical theoretical approaches assume a uniform stimulation of photosynthesis and growth across taxa. Direct assessments of the C balance either by flux studies or by repeated forest inventories also suggest a current net uptake, although magnitudes sometimes exceed those missing required to balance the global C cycle. Reasons for such discrepancies may lie in the nature of forest dynamics and in differential responses of taxa or plant functional types. In this contribution I argue that CO 2 enrichment may cause forests to become more dynamic and that faster tree turnover may in fact convert a stimulatory effect of elevated CO 2 on photosynthesis and growth into a long–term net biomass C loss by favouring shorter–lived trees of lower wood density. At the least, this is a scenario that deserves inclusion into long–term projections of the C relations of tropical forests. Species and plant functional type specific responses (‘biodiversity effects’) and forest dynamics need to be accounted for in projections of future C storage and cycling in tropical forests.

scholarly journals Long-term evolution of the global carbon cycle: historic minimum of global surface temperature at presen

Tellus B ◽  
2002 ◽  
Vol 54 (4) ◽  
pp. 325-343 ◽  
Author(s):  
Siegfried Franck ◽  
Konrad J. Kossacki ◽  
Werner Von Bloth ◽  
Christine Bounama
Keyword(s):  
Carbon Cycle ◽  
Surface Temperature ◽  
Global Carbon Cycle ◽  
Long Term Evolution ◽  
Global Surface Temperature ◽  
Term Evolution ◽  
Global Surface ◽  
Global Carbon

 Implementation of mycorrhizal mechanism into a soil carbon model improves the prediction of long-term processes of plant litter decomposition

2021 ◽  
Author(s):  
Weilin Huang ◽  
Peter van Bodegom ◽  
Toni Viskari ◽  
Jari Liski ◽  
Nadejda Soudzilovskaia
Keyword(s):  
Soil Carbon ◽  
Litter Decomposition ◽  
Arbuscular Mycorrhizae ◽  
Plant Litter ◽  
Climate Impacts ◽  
Microbial Interactions ◽  
Soil C ◽  
Plant Litter Decomposition ◽  
C Dynamics

<p>Mycorrhizae, a plant-fungal symbiosis, is an important contributor to below ground-microbial interactions, and hypothesized to play a paramount role in soil carbon (C) sequestration. Ectomycorrhizae (EM) and arbuscular mycorrhizae (AM) are the two dominant forms of mycorrhizae featured by nearly all Earth plant species. However, the difference in the nature of their contributions to the processes of plant litter decomposition is still understood poorly. Current soil carbon models treat mycorrhizal impacts on the processes of soil carbon transformation as a black box. This retards scientific progress in mechanistic understanding of soil C dynamics.</p><p>We examined four alternative conceptualizations of the mycorrhizal impact on plant litter C transformations, by integrating AM and EM fungal impacts on litter C pools of different recalcitrance into the soil carbon model Yasso15. The best performing concept featured differential impacts of EM and AM on a combined pool of labile C, being quantitatively distinct from impacts of AM and EM on a pool of recalcitrant C.</p><p>Analysis of time dynamics of mycorrhizal impacts on soil C transformations demonstrated that these impacts are larger at the long-term (>2.5yrs) litter decomposition processes, compared to the short-term processes. We detected that arbuscular mycorrhizae controls shorter term decomposition of labile carbon compounds, while ectomycorrhizae dominate the long term decomposition processes of highly recalcitrant carbon elements. Overall, adding our mycorrhizal module into the Yasso model greatly improved the accuracy of the temporal dynamics of carbon sequestration.</p><p>A sensitivity analysis of litter decomposition to climate and mycorrhizal factors indicated that ignoring the mycorrhizal impact on the decomposition leads to an overestimation of climate impacts. This suggests that being co-linear with climate impacts, mycorrhizal impacts could be partly hidden within climate factors in soil carbon models, reducing the capability of such models to mechanistically predict impacts of climate vs vegetation change on soil carbon dynamics.</p><p>Our results provide a benchmark to mechanistic modelling of microbial impacts on soil C dynamics. This work opens new pathways to examining the impacts of land-use change and climate change on plant-microbial interactions and their role in soil C dynamics, allowing the integration of microbial processes into global vegetation models used for policy decisions on terrestrial carbon monitoring.</p>

scholarly journals Soil organic matter turnover rates increase to match increased inputs in grazed grasslands

2021 ◽  
Author(s):  
Shane W. Stoner ◽  
Alison M. Hoyt ◽  
Susan Trumbore ◽  
Carlos A. Sierra ◽  
Marion Schrumpf ◽  
...  
Keyword(s):  
Climate Change ◽  
Management Practice ◽  
Turnover Rates ◽  
Decomposition Rates ◽  
Soil C ◽  
C Storage ◽  
Trade Offs ◽  
Soil Organic Matter Turnover ◽  
C Stocks

AbstractManaged grasslands have the potential to store carbon (C) and partially mitigate climate change. However, it remains difficult to predict potential C storage under a given soil or management practice. To study C storage dynamics due to long-term (1952–2009) phosphorus (P) fertilizer and irrigation treatments in New Zealand grasslands, we measured radiocarbon (14C) in archived soil along with observed changes in C stocks to constrain a compartmental soil model. Productivity increases from P application and irrigation in these trials resulted in very similar C accumulation rates between 1959 and 2009. The ∆14C changes over the same time period were similar in plots that were both irrigated and fertilized, and only differed in a non-irrigated fertilized plot. Model results indicated that decomposition rates of fast cycling C (0.1 to 0.2 year−1) increased to nearly offset increases in inputs. With increasing P fertilization, decomposition rates also increased in the slow pool (0.005 to 0.008 year−1). Our findings show sustained, significant (i.e. greater than 4 per mille) increases in C stocks regardless of treatment or inputs. As the majority of fresh inputs remain in the soil for less than 10 years, these long term increases reflect dynamics of the slow pool. Additionally, frequent irrigation was associated with reduced stocks and increased decomposition of fresh plant material. Rates of C gain and decay highlight trade-offs between productivity, nutrient availability, and soil C sequestration as a climate change mitigation strategy.

Consumption of residual pyrogenic carbon by wildfire

2013 ◽  
Vol 22 (8) ◽  
pp. 1072 ◽  
Author(s):  
C. Santín ◽  
S. H. Doerr ◽  
C. Preston ◽  
R. Bryant
Keyword(s):  
Forest Floor ◽  
Global Carbon Cycle ◽  
Stainless Steel Mesh ◽  
Major Mechanism ◽  
Pyrogenic Carbon ◽  
Mass Losses ◽  
Mesh Bags ◽  
The Subject ◽  
Global Carbon

Pyrogenic carbon (PyC) produced during vegetation fires represents one of the most degradation resistant organic carbon pools and has important implications for the global carbon cycle. Its long-term fate in the environment and the processes leading to its degradation are the subject of much debate. Its consumption in subsequent fires is considered a potential major mechanism of abiotic PyC degradation; however, no quantitative data supporting this removal pathway have been published to date. To address this gap, we quantified consumption of residual PyC at the forest floor during an experimental fire, representative of a typical boreal wildfire, complemented by exploratory laboratory heating experiments. Labelled PyC (pinewood charcoal from a slash pile burn), in granular form contained in stainless steel mesh bags and as individual pieces, were placed at ~2-cm depth within the forest floor. The median mass loss of granular charcoal was 6.6%, with 75% of the samples losing <15%, and of individual pieces 15.1% with 75% of the samples losing <25%. The mass losses under laboratory conditions, although somewhat higher than in the field, confirm an overall low consumption of PyC. The limited losses of PyC found here do not support the widely held notion that wildfire is a major cause of loss for residual PyC.

Simulating soil C dynamics with EPIC: Model description and testing against long-term data

2006 ◽  
Vol 192 (3-4) ◽  
pp. 362-384 ◽  
Author(s):  
R.C. Izaurralde ◽  
J.R. Williams ◽  
W.B. McGill ◽  
N.J. Rosenberg ◽  
M.C. Quiroga Jakas
Keyword(s):  
Model Description ◽  
Epic Model ◽  
Soil C ◽  
C Dynamics ◽  
Term Data

Long-term tillage systems impacts on soil C dynamics, soil resilience and agronomic productivity of a Brazilian Oxisol

2014 ◽  
Vol 136 ◽  
pp. 38-50 ◽  
Author(s):  
João Carlos de Moraes Sá ◽  
Florent Tivet ◽  
Rattan Lal ◽  
Clever Briedis ◽  
Daiani Cruz Hartman ◽  
...  
Keyword(s):  
Tillage Systems ◽  
Soil C ◽  
C Dynamics ◽  
Soil Resilience
Sign in / Sign up

Export Citation Format

Share Document